308 Sheep Pox. 



whereby a fine, bluish-white vesicle develops with a transparent 

 wall. This continues to enlarge on the following day, and at 

 the same time a slight depression (navel) develops on the top 

 (stad. vesiculosum; Fig. 54). The development of the vesicles 

 occurs in the same succession as is the case in the appearance 

 of the red spots and the nodules, and it may take several days 

 for the development of all the vesicles. The vesicles attain a 

 size ranging from that of a lentil to that of a bean; while the 

 larger vesicles are more flat and in their center the navel is 

 never absent, the smaller ones are less elevated, resembling 

 more blunt ended pins and on them the navel may frequently 

 be absent. The closer the vesicles are located to each other the 

 smaller their size, and vice versa. In pricking the vesicles their 

 serous contents ooze out slowly, on account of their compart- 

 ment-like construction. 



Immediately surrounding the vesicles the skin is as a 

 rule hyperemic, and therefore forms red zones around them; 

 the skin and the subcutaneous connective tissue of the 

 affected parts are also edematous, as a result of which the 

 respective regions of the body, especially the head, and on 

 this particularly the eyelids and the region of the nose are 

 swollen, so that the corresponding openings and slits become 

 constricted. The development of the exanthema up to this 

 degree usually takes from 5 to 6 days. 



In the completely developed ripe vesicles the clear yellowish 

 or pale red lymph-like contents changes after 2 to 3 days, or 6 to 

 7 days from the onset of the disease, into a cloudy fluid owing to 

 the admixture of pus cells, finally becoming entirely white, at 

 the same time the vesicle may increase somewhat in size and 

 the navel-like depression may also disappear (stad. pustulosum 

 s. suppurationis), while the edematous infiltration of the skin 

 in their immediate surroundings becomes as a rule still more 

 intense. This stage usually lasts three days. 



This completes the development of the vesicles; a depres- 

 sion again appears on their tops, the wall becomes withered and 

 wrinkled, and after the horny layer has taken on a brownish 

 color the vesicle dries with its contents to a %-l mm. thick 

 brown scab (stad. crustosum s. exsiccationis). N'ew epithelia 

 form under this from the borders and from the base of the 

 vesicle, whereupon the scab drops off in from 4 to 6 days (stad. 

 decrustationis). In its place a red spot or a red scar remains 

 for a time, which gradually turns pale and at the same time 

 becomes somewhat depressed. 



The development of the eruption is associated more or less 

 with severe general symptoms. The sudden high fever at the 

 onset of the disease diminishes from the second to third day 

 on, and in the pustular, as well as in the vesicular stage only 

 a moderate fever is present. With the appearance of suppura- 

 tion it again increases, and again drops rapidly after 2 to 3 

 days, so that the drying of the vesicles, as well as the falling off 

 of the scabs occurs under normal temperature. 



